A refined classification of SPEs based on the multienergy channel observations

Abstract

AbstractWe have investigated characteristics of solar proton events (SPEs) and their association with other types of solar eruption using 42 SPEs observed with SOlar and Heliospheric Observatory/Energetic and Relativistic Nuclei and Electron detector from 1997 to 2012. A velocity dispersion analysis was performed to correctly estimate the onset times of proton flux increase at the solar vicinity. These SPE onset times were compared with those of associated flares, coronal mass ejections (CMEs), and interplanetary type II radio bursts. We found that (i) the proton flux of 13 SPEs (31%) increase during the flare X‐ray intensity is increasing, and the rest 29 SPEs (69%) show onsets well coincident with the first appearance of CMEs in Large Angle and Spectrometric COronagraph field of view. (ii) All flare‐associated SPEs show the flux enhancements starting from the lower energy, while the CME‐associated SPEs show the flux enhancements starting from either the higher or the lower energies. In the other events, the flux enhancement occurs simultaneously at all energies within 10 min. (iii) For the former, large flux enhancements occur in a short time, while the latter tend to show relatively weak and slow flux enhancements. Our classification uses two criteria, SPE onset timing relative to flares and energy‐dependent flux enhancement, unlike the conventional classification of SPEs based on whether the flux time profile is impulsive or gradual. Nevertheless our classification scheme refines the distinction between the flare‐associated SPEs and the CME‐associated SPEs in terms of the onset timing. Additional information on the proton acceleration as implied by the energy‐dependent patterns of flux enhancement is briefly discussed.